As the mobile communication industry and the information electronic industry have been developed markedly in recent years, lithium secondary batteries with high capacity and low weight have been increasingly in demand. However, since mobile instruments have become more multi-functionalized, energy consumption thereof increases, and thus batteries used in such instruments as drive sources have been required to be provided with higher power and capacity. Additionally, active and intensive research and development have been conducted to substitute cobalt (Co), which is expensive and limited in supply, with inexpensive nickel (Ni), manganese (Mn), iron (Fe) or the like.
However, LiMn2Co4 provides a lower battery capacity when compared to LiCoO2 by about 20% and shows a problem of Mn dissolution at higher temperature. Additionally, LiNiO2 provides an improved energy density when compared LiCoO2, but shows a safety-related problem. Further, LiFePO4 provides a lower capacity when compared to LiCoO2 by about 20% and shows a problem related to C-rate characteristics.
In the case of an electrode active material having a gas generation plateau potential in a charging period, there has been the following problem: when a battery is charged to such an extent that gas generation does not occur yet, the battery shows a low capacity, and when a battery is charged to such an extent that gas generation occurs, the battery itself cannot be realized due to the gas generation.